What is a VCUG?
A voiding cystourethrogram (VCUG) is a test in which the bladder is filled with contrast dye and followed with X-rays. Images are taken while the bladder fills and while the child passes urine.
What does it show?
- Vesicoureteral reflux (VUR): whether urine flows back into the ureters and the kidney, and the grade,
- the urethra: in boys, posterior urethral valves, narrowings,
- the shape of the bladder: wall thickening, diverticula, ureterocele,
- how the bladder empties.
When is it needed?
- widening of the ureters on ultrasound, or severe hydronephrosis on both sides,
- suspected valves in a boy,
- recurrent or atypical febrile urinary tract infection,
- monitoring reflux or checking the result after treatment.
How is it done?
- The child lies on the X-ray table, and the genitals are cleaned with a sterile solution.
- A very thin, soft catheter is placed through the urethra into the bladder. This may cause brief discomfort, but it is not painful.
- The contrast dye slowly fills the bladder, and images are taken.
- When the bladder is full, the child passes urine on the table, and images of the urethra are taken at that moment.
Preparation
- Fasting is not needed.
- Explain the test to your child in simple words suited to his or her age.
- Bring a favorite toy or tablet.
- Your child must not have a urinary tract infection at the time of the test. The doctor sometimes prescribes a short course of antibiotics.
Afterward
- Drink plenty of fluids.
- There may be mild burning when passing urine for 1–2 days.
- If there is a fever, see a doctor.
When to seek urgent care
If any of the following is present, do not wait for a routine appointment: call the doctor or go to the nearest emergency department.
- Fever within 1–3 days after the test
- Unable to pass urine
Note for pediatricians and family doctors
VCUG is the gold standard for diagnosing VUR and posterior urethral valves. It is done after an active infection has been treated; some centers give short antibiotic prophylaxis before and after the procedure. Images during the voiding phase are mandatory to see the urethra, especially in boys. The radiation-free alternative is contrast-enhanced voiding urosonography (ceVUS).
What happens at the visit?
- The test is scheduled for a time when there is no active infection.
- The procedure is explained to the child and parent in advance.
- The doctor assesses the result together with the child's other tests.
Frequently asked questions
Is my child given medicine to calm down?
Usually it is not needed. Having a parent nearby, a calm explanation and a toy help. In some cases a mild sedative may be used.
Is there an alternative without radiation?
Some centers use voiding urosonography with ultrasound contrast (ceVUS). It shows reflux well, but may not show the urethra as clearly as X-ray.
Related topics
- Vesicoureteral refluxUreteral reflux, VURCondition
- Posterior urethral valvesCongenital membrane in the urethra, PUVCondition
- HydronephrosisWater on the kidney, dilated renal pelvisCondition
- Urinary tract infectionBladder infection, cystitisCondition
- Kidney and bladder ultrasoundUltrasound scan, sonographyTest
Sources
- EAU Guidelines on Paediatric Urology, 2025.
- Riccabona M et al. ESPR uroradiology task force: imaging recommendations in paediatric uroradiology. Pediatr Radiol, 2008.
This page is for education. Decisions about your child’s treatment are made together with the doctor after an examination.